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Biomedical subjects

R Martin

Publications and source records attributed to R Martin.

At least 469 records · Page 26Linked to original sources
PubMed1990

L5178Y mouse lymphoma cell mutation assay results with 41 compounds.

Forty-one chemicals were tested for their abilities to induce trifluorothymidine resistance in L5178Y mouse lymphoma (MOLY) cells. These chemicals were included in the National Toxicology Program's evaluation of four in vitro short-term toxicity assays for predicting carcinogenicity in the rodent bioassay. Of the 41 chemicals examined for this report, 8 were equivocal in the rodent bioassay, and 7 were questionable in- the MOLY assay. If these chemicals are eliminated from an analysis of concordance, the remaining 26 chemicals lead to a concordance of 69% with a sensitivity of 71%. The specificity could not be determined because only two non-carcinogens were detected.

Animals↗
PubMed1990

Borrelia burgdorferi myelitis presenting as a partial stiff man syndrome.

Eight weeks after a tick bite, a 33-year-old male patient presented with stiffness of one leg together with spasmodic painful jerks resembling stiff man syndrome. Isolated myelitis of lumbosacral segments of the spinal cord, apparently confined to the grey matter, was diagnosed and its spirochaetal aetiology confirmed by serology and CSF findings. Oligoclonal IgG bands in CSF specific for Borrelia burgdorferi were found. Thus, there is evidence that B. burgdorferi ist able to cause a localized myelitis, probably of spinal interneurons, presenting as a partial stiff man syndrome.

Adult↗
PubMed1990

Mutagenic and genotoxic activities of extracts derived from the cooked and raw edible mushroom Agaricus bisporus.

A. bisporus has been reported to be carcinogenic to mice [Toth et al. (1986) Cancer Res 38:177-180] and mutagenic in Salmonella typhimurium [Sterner et al. (1982) Mutat Res 101:269-281]. The effects of different heat treatments on the mutagenicity of raw, cooked (boiled) and fried A. bisporus extracts in the S. typhimurium test is reported. The spectrum of potential mutagenic activity of A. bisporus extracts was tested in vitro in Syrian hamster embryo cells for selective DNA amplification and in primary rat hepatocytes for DNA single-strand breaks. DNA single-strand breaks were also determined in liver cells of rats and micronuclei were measured in bone marrow cells of mice in vivo following oral application of A. bisporus extracts. It was shown that the complex A. bisporus extracts per se are not detectably mutagenic in S. typhimurium and that the previously observed increase in number of colonies per plate is probably due to a histidine artefact. No indication of genotoxicity was seen in the two in vitro assays with primary mammalian cells with two different end points. No evidence of in vivo genotoxic effects was observed in the rat liver cells. Finally, A. bisporus was not genotoxic in the micronucleus assay of mouse bone marrow cells in contrast to its previously reported carcinogenicity in mice.

Agaricus↗
PubMed1990

Clinical, electrical and mechanical correlations during recovery from neuromuscular blockade with vecuronium.

In order to determine correlations between electromyographic (EMG), mecanomyographic (MMG) and clinical criteria of adequate recovery from neuromuscular blockade with vecuronium, seven young healthy conscious volunteers were given subparalysing doses of vecuronium. During recovery from neuromuscular blockade, vital capacity, negative inspiratory pressure, peak expiratory flow rate and five-second head lift were assessed. Neuromuscular monitoring included the evoked EMG response of the adductor digiti minimi and the simultaneous evoked MMG response of the adductor pollicis on the same side. We found that all subjects maintained head lift for five seconds at EMG T4T1 of 0.70, and they achieved normal respiratory tests at EMG T4/T1 of 0.90. The MMG T4/T1 needed for the subjects to perform normal respiratory tests was found to be 0.50, at which time six of the seven subjects were able to perform adequately the head lift test.

Adult↗
PubMed1990

Clinical assessment of the muscular response to tetanic nerve stimulation.

The study was undertaken in order to determine clinical tactile evaluation of tetanic nerve stimulation (50 Hz, 5 sec) as a means of detecting fade and possible residual curarization. Forty-four patients were studied and 128 clinical evaluations by eight different observers were performed at various levels of neuromuscular blockade. Tetanic fade was detected reliably by clinical evaluation only when high degrees of fade (tetanic fade ratio of 0.3 or less) were detected with a force-displacement transducer. We conclude that the clinical tactile assessment of the response to tetanic stimulation is not accurate except at very high degrees of fade and that its usefulness in monitoring neuromuscular recovery is doubtful.

Adult↗
PubMed1990

Visualization of differential neurofilament phosphorylation in the pre- and postsynaptic axoplasm of the squid giant synapse: an electron spectroscopic study.

When inelastically scattered electrons with an energy loss specific for interaction with phosphorus atoms were used for visualization of sections of squid axons, bead-like domains of elongated proteins, presumably neurofilaments, exhibited distinct phosphorus signals. A marked asymmetry of these phosphorus signals was detectable between the pre- and the postsynaptic cytoskeleton of the giant synapse. Signals were very numerous and intense in the presynaptic terminal, while rare and weak in the postsynaptic axoplasm. The giant axon revealed a delayed appearance of phosphorus signals in its course from the cell bodies in the giant fibre lobe to its exit from the stellate ganglion. Numerous and intense phosphorylation signals were evident only in the peripheral giant axon. Asymmetry in the distribution of phosphorus signals between pre- and postsynaptic axoplasm paralleled differences in Ca(2+)-buffering mechanisms, as shown in a previous study. In the presynaptic terminal patterns of phosphorus signals correlated with precipitates which had formed after intra-axonal injection of calcium. Our observations suggest a role of phosphorylated neurofilaments in binding of calcium in the squid synapse.

Animals↗
PubMed1990

Neurons in the inferior colliculus of cats sensitive to sound-source elevation.

The sensitivity to variations in sound-source elevation was studied in 48 units, previously examined as to their azimuthal sensitivity, of the inferior colliculi of cats. Of these units, 36 were directionally-sensitive (firing rate varied by more than 50% across the range of positions studied) to both azimuthal and elevational changes. Elevation sensitivity was common to noise stimuli (19/25 units) and pure tones in excess of 6 kHz (17/17 units). Not one of the 8 azimuth-sensitive units with CFs below 6 kHz was directionally-sensitive to the elevation of CF stimuli. The 4 units omnidirectional to azimuthal variation were similarly insensitive to elevation. The shapes of functions relating sound-source elevation to spike count (elevation functions) varied across an apparent continuum, with some very sharply-peaked functions being observed. Peak spike counts almost invariably occurred at stimulus elevations above the horizontal plane. Comparisons of the widths of elevation and azimuth functions at the same sound pressure level were made for 36 units. The relative sharpness of elevation and azimuthal tuning varied across the population. The common association of sensitivity to both azimuth and elevation suggests that elevation sensitivity may be mediated partly by binaural comparisons.

Acoustic Stimulation↗
PubMed1990

Free radical scavenging and cytotoxic properties in the ellipticine series.

In the series of cytotoxic intercalating compounds derived from ellipticine, we tried to correlate free radical scavenging properties with cytotoxic activities. Scavenging properties were determined in vitro on two experimental models: a) antioxidant activity of the drugs during the autoxidation of methyl linolenate induced by azo-bis-isobutyronitrile; this activity was measured either by the initial rate ratios in the presence and in the absence of the drug or by the length of the inhibition period of the reaction in the presence of the drug and b) ability to reduce DPPH free radicals. Cytotoxic properties were expressed by ID50 the dose which reduces by 50% the L 1210 cell growth rate as compared to controls after 48 h. It appears that antioxidant activity and reduction of DPPH both require the presence of a free OH group on the ellipticine ring. A good correlation is observed between cytotoxicity and antioxidant activity of the hydroxylated derivatives; minor structural modifications which result in a loss of cytotoxic activity also result in a loss of antioxidant properties. No such correlation is observed with DPPH reducing properties of ellipticine derivatives.

Alkaloids↗
PubMed1990

Multiple sclerosis in Spain: an epidemiological study of the Alcoy health region, Valencia.

Alcoy is a defined health region in eastern Spain, at 3 degrees E-38 degrees N, with a single neurology department and includes 33 towns with a total population of 133,915 inhabitants. We have evaluated the prevalence and incidence of multiple sclerosis (MS) by analysing this region. Six new cases have been detected (2.24/100,000/year) and the prevalence rate was 17.17/100,000, the highest in Spain at the moment. However, we found an irregular distribution in the different towns in so far that 15 of our 23 patients lived in a particular subregion, which means a prevalence of 44.59/100,000. Our study shows that the area of Alcoy is a medium MS risk region according to the thesis of Kurzke, although high MS areas may be found, thus confirming that MS distribution in southern Europe is not uniform.

Adult↗
PubMed1990

Ischemic stroke in young adults. II. Analysis of risk factors in the etiological subgroups.

A prospective study on 386 consecutive patients affected of ischemic stroke (IS) has been analysed in relation to etiologies, comparing them with a control group of 100 people. The atherotrombotic etiology subgroups are associated with family history of stroke, risk factors, atheromatosis, occlusive peripheral arteriopathy, previous of stroke, high levels of hematocrit and hemoglobin, impaired lipid fractions and high levels of uric acid. The cardiac embolism etiology subgroups are associated with the presence of personal history of stroke, just as the mitral valva prolapse (MVP) patients group. The migraine group is significantly related with the intake of oral contraceptives.

Adult↗
PubMed1990

Q fever in Sokoto, Nigeria.

There is very little information available about the prevalence of Coxiella burnetii in Africa. We obtained blood from 75 Nigerians hospitalized in Sokoto for a variety of acute medical conditions. Their age range was 7 months to 50 years; there were 39 males and 36 females. Antibody titers were determined to phase I and phase II C. burnetii antigens using a microimmunofluorescence test. Thirty-three (44%) had an antibody titer of greater than or equal to 1:8 to phase II C. burnetii. We conclude on the basis of this limited survey that Q fever is common in Nigeria.

Adolescent↗
PubMed1990

Butyrate esterase (4-methylumbelliferyl butyrate) spot test, a simple method for immediate identification of Moraxella (Branhamella) catarrhalis [corrected].

A total of 47 Moraxella (Branhamella) catarrhalis strains, 89 strains of Neisseria spp., and 82 strains of miscellaneous bacteria and yeasts were studied by using a fluorogenic spot method which detects butyrate esterase. A positive butyrate esterase spot test correctly differentiated M. catarrhalis from Neisseria spp., which had a negative butyrate esterase spot test reaction. The test is rapid, simple, and easy to perform. The butyrate esterase spot test was useful for direct identification of M. catarrhalis from primary cultures. However, false-positive reactions may occur with mixed cultures.

Bacteriological Techniques↗
PubMed1990

Weight cycling in female rats subjected to varying meal patterns.

The effect of weight cycling on energy balance was examined in female rats. Two groups of adult female rats were subjected to three bouts of weight cycling, each bout consisting of 8 days of food restriction (9 g/day or approximately 50% of usual intake) followed by 16 days of refeeding. During refeeding animals were given 22.8 g/day of food so that they were offered, during the 24-day cycle, the same amount of food offered to control rats that were not subjected to weight cycling. One group of weight-cycled rats (gorgers) was given its daily intake in a few large meals (i.e., allowed to gorge). The other weight-cycled group (nibblers) was fed by automated feeders in several small meals during each 24-h period (i.e., prevented from gorging). Neither weight-cycled group displayed an increased food efficiency or an increased body fatness compared with noncycled controls. Weight-cycled rats allowed to gorge did have an increased food efficiency and a greater carcass energy content compared with weight-cycled rats not allowed to gorge. These results suggest a pattern of gorging promoted food efficiency and body energy gain compared with a pattern of nibbling, but gorging during refeeding cannot account for reports of increased food efficiency in weight-cycled rats.

Adipose Tissue↗
PubMed1990

Thalamic single-unit activity occurring in patients with hemidystonia.

Lesions of the ventrolateral complex of the human thalamus may relieve abnormal movements in patients with dystonia. We have now recorded the thalamic single-unit activity and the electromyographic (EMG) activity in the upper extremity during the physiologic localization which is required prior to thalamotomy for hemidystonia. The activity of thalamic single units was correlated with the EMG signal by spectral methods. Results of this analysis indicate that a group of thalamic cells show a concentration of activity, occurring at the same frequency as the EMG activity during dystonia. In many cases, there was statistically significant correlation between thalamic and EMG signals at the frequency of dystonia. The activity of these cells may be involved in the generation of dystonic movements.

Dominance, Cerebral↗
PubMed1990

Complex visual disturbances in Alzheimer's disease.

Although Alzheimer's disease (AD) involves visual association cortex, previous studies have not systematically investigated complex visual disturbances in AD. We examined 30 community-based AD patients, 13 (43%) of whom had complex visual complaints, and compared them with 30 controls on 7 types of complex visual tasks. Despite preserved visual acuity and color recognition, the AD patients were impaired in the visual evaluation of common objects, famous faces, spatial locations, and complex figures. In the AD patients, we found that all 30 had disturbances in figure-ground analysis; 17 (57%) had difficulties visually recognizing actual objects ("agnosia"); those with worse dementia disability had the most complex visual disturbances; and a subgroup (6) with Balint's syndrome performed the most poorly on the complex visual tasks. This study demonstrates that a range of complex visual disturbances are common in AD and suggests that they may result from the known neuropathology in the visual association cortex.

Aged↗
PubMed1990

A highly sensitive, nonradioactive DNA labeling and detection system.

A highly sensitive method for detecting specific nucleotide sequences was recently developed. The method uses digoxigenin-labeled nucleic acid probes for hybridization to immobilized target nucleic acids. Probes can be labeled by the random-primed method, nick translation, oligonucleotide tailing, cDNA synthesis, photodigoxigenin or SP6/T7/T3 polymerase-mediated transcription. Hybrids are detected by an enzyme-linked immunoassay using an anti-digoxigenin antibody conjugate. Visualization of the bound antibody is accomplished by an enzymatic color reaction, enzymatic chemiluminescent reaction or immunofluorescence, depending on the antibody conjugate and enzymatic substrate used. Here we report the successful application of this technology in the detection of specific cloned DNA in colony and plaque hybridizations, specific detection of a single mRNA species in Northern blots and single-copy gene detection in genomic Southern blots.

Bacteriophage lambda↗